Hollingworthite is a rare platinum-group mineral typically occurring as microscopic inclusions within other platinum-group alloys or sulfide ores. Collectors rarely encounter it as hand specimens, as it is usually found via micro-analysis of ore samples from large igneous complexes.
Is this hollingworthite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch hollingworthite with a known reference. Hollingworthite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Hollingworthite leaves a grayish-black streak.
- 3Read the lusterHold the specimen under a strong light. Hollingworthite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silver-white, light-gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral grains, inclusions in platinum-group minerals.
Often confused with
Hollingworthite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Hollingworthite leaves grayish-black, Cobaltite leaves greyish-black.
How to tell apart: Streak differs — Hollingworthite leaves grayish-black, Sperrylite leaves black.
Often found alongside hollingworthite
Minerals reported to co-occur with hollingworthite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Rh,Pt,Pd)AsS
- Mohs hardness
- 6
- Density
- 9.5-10.0 g/cm³
- Colors
- Streak
- Grayish-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Anhedral Grains, Inclusions in Platinum-group Minerals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific Study
- Host rock
- Mafic and Ultramafic Igneous Rocks
- Typical price
- $50-500 depending on specimen size and purity
Where rockhounds find hollingworthite
Classic worldwide localities
- Bushveld Complex, South Africa
- Stillwater Complex, USA
- Norilsk, Russia
- Sudbury, Canada
Field-hunting tip
Look in mafic and ultramafic igneous rocks country — that is the host setting where hollingworthite typically forms. If you start seeing platinum, palladium, sperrylite in float, you are in the right ground. Field specimens usually show a anhedral grains, inclusions in platinum-group minerals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find hollingworthite on the map
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